says @sebdeh of Playfish. And according to Zynga general manager Roy Sehgal, the number of players returning regularly (and not play time) is the metric that most closely correlates to a social game’s suitability for monetization.

Having monetizability in mind during the initial stages of game design helps, but the fact is that unless you have love, you have no business asking your players for money.

Ads may cover some costs, but only rarely to any significant extent.

But even when there is love, measuring just about everything and continuously redesigning and innovating the gameplay and monetization tactics from day one is what brought companies such as Zynga, Playdom, Playfish and others their immense success.

And this is only the beginning – social games are forecast to be a 1.5 billion dollar industry in 3 years, and even today, the number of unique monthly players on Facebook alone surpasses 55 million.

At my company Motiviti, we are keeping all of this in mind and we realize that in order to thrive in the casual/social games market, we need to put all of our efforts in creative innovation and sound execution. And as we prepare to launch our first games for the iPhone and the browser, we are humbly trying to learn from the best and the brightest in this young industry at Casual Connect in Seattle.

Follow me and the hash tag #casualconnect on Twitter if you want to discuss Unity 3D, Flash and social network game development.